1. Field of the Invention
The present invention relates to an automatic open-and-close system for a vehicle slide door which transmits a drive force from a drive source to a slide door through an electromagnetic clutch to move the slide door for its opening/closing.
2. Description of the Related Art
There is known a control system for automatically opening and closing, by use of a drive source, e.g., a motor, a slide door which is mounted on the side of a vehicle body while being slidable in the lengthwise direction. To drive the slide door for its opening/closing, suitable operation means is located near the driver seat or the door handle, and the occupant intentionally operates the operation means.
When a vehicle stops at a sloped road, the automatic open-and-close system controls, by the controller contained therein, a power transmission maintenance force of the electromagnetic clutch, which is located between the drive source and the slide door, so as to inhibit the slide door from moving or to allow a manual operation for opening/closing the door.
The conventional system suffers from the following problems. The performances of the battery for supplying electric power to the controller are degraded by aging or other causes. When the engine of the vehicle carrying such a battery is started up, the output voltage of the battery will decrease, so that it fails to drive the controller. Where the controller is inoperative, the electromagnetic clutch is put in an off state, and the slide door moves down by its weight when the vehicle stops on the sloped road.
In the automatic open-and-close system using a microcomputer for the controller, when the power voltage drops, the microcomputer is reset in order to prevent the microcomputer from operating uncontrollably. Also in a case where the battery voltage is decreased below its normal voltage but it is high enough for the clutch to hold the slide door, the microcomputer is reset. The controller is inoperative and the electromagnetic clutch will be disengaged.
Some of those known systems are designed such that when the battery voltage drops to below a predetermined voltage, the systems automatically stop their operations. Each system monitors the battery voltage when no load is connected to the battery. The battery, although its performances are degraded, apparently produces a voltage approximate to the normal voltage because of its nature. In a case where the battery voltage drops after the slide door is driven, and the engine is started up when the slide door is moving, the battery voltage drops upon the starting up of the engine and the controller is reset.